BRAF, NRAS and KIT sequencing analysis of spindle cell melanoma

Background Spindle cell melanoma represents a rare but distinct subset of melanoma, and its genomic spectrum has not been fully defined. Methods We searched our institutional database for patients with a diagnosis of pure spindle cell-type melanoma whose tumors had been analyzed for BRAF, NRAS, and KIT mutations using pyrosequencing technique. Results We identified 24 patients with spindle cell melanoma, including 10 patients with desmoplastic melanoma, whose tumors had been analyzed for at least one of the three genes. The median Breslow thickness was 2.6 mm, and the most common site of the primary melanoma was the trunk, followed by the head and neck region. BRAF, NRAS and KIT genomic sequencing was performed successfully in 20, 18 and 14 patients, respectively. Among the 20 melanomas with completed BRAF-sequencing analysis, 6 (30%) harbored a mutation, of which 5 (83%) had a V600E mutation and 1 (17%) had a V600R mutation. None of the melanomas harbored NRAS or KIT mutations. Conclusion As has been reported in other common types of melanoma, V600 BRAF mutation is the most common mutation of those tested in spindle cell melanoma. NRAS or KIT mutation appears to be rare, if not completely absent.